Carbon fluoride as used in the present invention is to be distinguished from polymerized fluorinated hydrocarbons. The material itself is well known. It is formed by the reaction of carbon or graphite with fluorine or a fluorine compound at a relatively high temperature e.g. about 500.degree. C. The product is a compound having a variable molar ratio of fluorine to carbon atoms and is sometimes characterized as having the formula CF.sub.x. It is particularly useful because of its electrical insulating properties and its relatively inert character. It is not wetted by water and oil and consequently, repels those materials from a surface to which it has been applied. It also has self-lubricating properties at relatively high temperatures up to about 500.degree. C. Consequently it is a very useful material for many applications such as pumps, molds for plastic parts, ball and butterfly valves for the oil and gas industries, carburetor choke shafts and the like.
Electroless deposition of metals from aqueous solutions is well known in the art. An example is electroless nickel plating, which is particularly useful in connection with the present invention. A plating bath of this type contains at least four ingredients, namely, a source of nickel ions, a hypophosphite compound as a reducing agent, an acid or hydroxide pH adjusting compound and a complexing agent for the metal ions to prevent their premature precipitation.
It would be desirable to use a single bath in order to deposit both carbon fluoride particles and metal in combination to provide the properties available from each. In U.S. Pat. No. 3,617,363 various wear reducing particles were added to an electroless plating bath in order to improve the properties of the resulting co-deposited surface. These particles included molybdenum disulfide and silicon carbide and various other materials such as kaolin, plastic resins, metal oxides and other compounds including fluorides of many metals. However, there is no suggestion that carbon fluoride was contemplated.
In U.S. Pat. No. 3,765,925 the use of carbon fluoride in a plating bath is disclosed. However, in this case the bath is formulated for electrolytic deposition and consequently the properties of the materials and the composition of the bath differ from those of the present invention. A number of dispersion promoting additives for the carbon fluoride are suggested. Typical additives were characterized as being water soluble high molecular weight compounds, water soluble organic solvents and colloidal oxides. There is no suggestion, however, of the materials used in the bath of the present invention. In the related U.S. Pat. No. 3,787,294, however, a combination of various surfactants was indicated to be useful in connection with an electrolytic as opposed to electroless plating bath for depositing carbon fluoride along with metal. The surfactants used in such bath were characterized as being selected from the group comprising cationic surfactants, nonionic surfactants and amphoteric surfactants which exhibit cationic characteristics at the pH value of the particular plating bath employed. It is evident from this disclosure that the characteristics of the electrolytic plating process are significantly different from those the present invention as will be seen in the disclosure below.
In U.S. Pat. No. 4,098,654 an electrolytic plating process is used to deposit polyfluorocarbon resin particles and metals together and in which both cationic and non-ionic fluorocarbon surfactants are employed.
In a recent disclosure in West German Published Application No. DE3333121, electroless deposition as well as electrolytic deposition of carbon fluoride along with metals is disclosed. From the material claimed it would appear that the method is primarily directed to the use of polytetrofluoroethylene and consequently, only to a secondary extent to carbon fluoride. Nevertheless, a significant difference exists between the method disclosed by the German applicants and that of the present invention since it appears that the cationic and non-ionic surfactants used are significantly different and in different proportions than those which are required by the present invention. Consequently, there is no suggestion of the important factors which have been found to pertain to the electroless plating of carbon fluoride and metals together.